Mississippi Science GEN.1B.3
The Standard
- GEN.1B
- Students will analyze how the DNA sequence is copied and transmitted to new cells.
Microscopically observe and analyze the stages of the cell cycle (G1-S-G2-M) to describe the phenomenon and identify methods at different cell cycle checkpoints through which the integrity of the DNA code is maintained.
2026 Mississippi College- and Career-Readiness Standards for Science · Structure and Function of DNA
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students use microscope images to identify interphase and stages of mitosis. They describe what happens in G1, S, and G2, then explain how checkpoints stop a cell from dividing when DNA is damaged or chromosomes are not properly attached.
What Mastery Looks Like
- A student can label visible mitotic stages in an onion root tip image and group other cells as interphase. They know a basic light microscope cannot show whether an interphase cell is in G1, S, or G2. They can explain why the G2 checkpoint stops a cell with damaged DNA before mitosis.
Common Misconceptions
- Students may think they can see DNA being copied or tell G1 from S in a basic light micrograph. They may also think a checkpoint repairs DNA itself, rather than pausing the cycle while repair occurs.
How to Assess It
- Give students an onion root tip image with cell A in metaphase and cell B in interphase. Ask them to identify what they can see, explain why B cannot be assigned to G1, S, or G2 by sight, and name the checkpoint that stops damaged DNA from entering mitosis.
Lesson moves
Ways to Teach It
Have pairs sketch three onion root tip cells under a microscope, label visible mitotic stages, and tally interphase versus mitotic cells.
Ask students to write two sentences answering: If DNA copying finishes with an error, what should happen before mitosis?
Have students match cards showing DNA damage before copying, incomplete copying, and unattached chromosomes to G1, G2, and M checkpoints.
Show a diagram of UV-damaged skin cell DNA and ask why the cell should pause before copying it.
Keep exploring
Related Standards
- GEN.2B.4
Investigate the role of mutations and the loss of cell cycle regulation in the development of cancers.
- GEN.2B.3
Describe cellular mechanisms that can help to minimize mutations (e.g., cell cycle checkpoints, DNA polymerase proofreading, and DNA repair enzymes).
- BIO.1E
Students will develop and use models to explain the role of the cell cycle during growth, development, and maintenance in multicellular organisms.
- BIO.1E.2
Identify and describe the changes that occur in a cell during the cell cycle. Explore problems that might occur if the cell does not progress through the cycle ...
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